1. Field of the Invention
The present invention relates to an image forming apparatus such as copying machines, printers, etc. of an electrophotographic system and of an electrostatic storage system.
2. Related Background Art
A conventional image forming apparatus will be explained with reference to FIG. 6.
FIG. 6 is a schematic side view showing an entire printer defined as the conventional image forming apparatus. This printer is constructed so that the image forming section forms electrostatic latent images by light of images formed based on image signals transmitted from an unillustrated controller part, and then forms color visible images by developing the electrostatic latent images and transferring visible images in superposition. The color visible images are transferred onto a transferring material (a material for recording) such as a recording sheet, etc., and the color visible images on the transferring material are fixed by a fixing section.
Referring to FIG. 6, the symbol P represents a printer, the numeral 1 designates a transferring material (recording material) housing cassette (containing cassette), and the numeral 2 denotes the transferring material. The transferring material housing cassette 1 houses plural sheets of transferring materials. The numeral 3 stands for an image forming part constructed of photosensitive bodies 4Y, 4M, 4C, 4K provided with respective stations side by side for development colors (yellow (Y), magenta (M), cyan (C), black (K)), injection chargers 5Y, 5M, 5C, 5K serving as primary charging means, developing units 6Y, 6M, 6C, 6K serving as developing means, toner cartridges 7Y, 7M, 7C, 7K, an intermediate transferring body 8, a sheet feeding section, a transferring section and a fixing section 9.
The photosensitive bodies 4Y, 4M, 4C, 4K, the injection chargers 5Y, 5M, 5C, 5K and the developing units 6Y, 6M, 6C, 6K are mounted in process cartridges 10Y, 10M, 10C, 10K detachably attached to a body of the image forming apparatus.
The photosensitive bodies 4Y, 4M, 4C, 4K each taking a drum-like shape are constructed by coating organic photo-conductive layers over outer peripheries of aluminum cylinders and are rotated by unillustrated drive motors. The drive motors rotate the photosensitive bodies 4Y, 4M, 4C, 4K counterclockwise in FIG. 6 in accordance with an image forming operation. Beams of light, to which the photosensitive bodies 4Y, 4M, 4C, 4K are exposed, are traveled from scanner parts 11Y, 11M, 11C, 11K, and surfaces of the photosensitive bodies 4Y, 4M, 4C, 4K are selectively exposed to the beams of light, thereby forming electrostatic latent images.
The primary charging means has a structure in which each station is provided with four pieces of injection chargers 5Y, 5M, 5C, 5K for electrifying the photosensitive bodies 4Y, 4M, 4C, 4K for yellow (Y), magenta (M), cyan (C) and black (K), and the respective injection chargers 5Y, 5M, 5C, 5K are provided with sleeves 5YS, 5MS, 5CS, 5KS.
The developing means has a structure in which each station is provided with four pieces of developing units 6Y, 6M, 6C, 6K for developing in yellow (Y), magenta (M), cyan (C) and black (K) in order to visualize the electrostatic latent images, and the respective developing units 6Y, 6M, 6C, 6K are provided with sleeves 6YS, 6MS, 6CS, 6KS. The developing units 6Y, 6M, 6C, 6K are detachably attached to the body of the image forming apparatus.
The intermediate transferring body 8 abuts the photosensitive bodies 4Y, 4M, 4C, 4K and, when forming color images, rotates clockwise in FIG. 6 as the photosensitive bodies 4Y, 4M, 4C, 4K make rotations, thus transferring the visible images onto the intermediate transferring body 8. Further, when forming the images, transferring rollers 12a which will be explained later on are brought into contact with the intermediate transferring body 8, whereby the transferring material 2 is conveyed while being nipped in between the transferring rollers 12a and the intermediate transferring body 8. The color visible images can be transferred in superposition onto the transferring material 2 and the intermediate transferring body 8, simultaneously.
The transferring rollers 12a abut intermediate transferring body 8 while transferring the color visible images in superposition onto the intermediate transferring body 8. When finishing the print processing, however, the transferring rollers 12a are shifted to positions 12b depicted by a broken line in FIG. 6, thus separating the transferring rollers 12a from the intermediate transferring body 8.
The fixing section 9 fixes the transferred color visible images onto the transferring material 2 while conveying the transferring material 2. The fixing section 9 includes fixing rollers 13 for heating the transferring material 2, and pressurizing rollers 14 for bringing the transferring material 2 into a press-contact with the fixing rollers 13. The fixing roller 13 and the pressurizing roller 14 are hollowed and are provided with heaters 15, 16 respectively in their interiors. Namely, the transferring material 2 bearing the color visible images is conveyed by the fixing rollers 13 and the pressurizing rollers 14 and is heated and pressurized, whereby the toners are fixed onto the surface of the transferring material 2.
The transferring material 2 is, after the visible images have been fixed onto the material 2, discharged to the outside of the apparatus from a discharging part, thereby finishing the image forming operation.
The printer P manages a conveying state of the transferring material by use of a lower-stage conveyance sensor 17, an upper-stage conveyance sensor 18, a lower-stage conveyance sensor 19, an upper-stage conveyance sensor 20, a registration sensor 21, a pre-fixing sensor 22, a fixing discharging sensor 23 and a discharging sensor 24, which are disposed on a transferring material conveying path.
The numeral represents a cleaning means for cleaning residual toners on the photosensitive bodies 4Y, 4M, 4C, 4K and on the intermediate transferring body 8. Waste toners after transferring onto the intermediate transferring body 8 the visible images formed by the toners on the photosensitive bodies 4Y, 4M, 4C, 4K or waste toners after transferring onto the transferring material 2 the four-color (Y, M, C, K) visible images formed on the intermediate transferring body 8, are accumulated in an unillustrated cleaner container.
The numeral 26 designates a discharging option including rollers 27, 28, 29, 30, a flapper 31, a first discharging bin 32, a second discharging bin 33, a third discharging bin 34 and a bin ascending/descending motor 35.
The discharging option 26 serves to sort out the transferring materials 2 by use of the first discharging bin 32, the second discharging bin 33 and third discharging bin 34 and to thus stack the materials 3 up. The discharging bins 32–34 are moved up and down by the bin ascending/descending motor 35, thereby sorting out the transferring materials 2 into the respective bins 32–34. The flapper 31 serves to change over the surface and the undersurface of the transferring material 2 fed to the discharging option 26 on the basis of an instruction given from the controller part. If a face-up designation is given from the controller part, the transferring material 2 is led to the rollers 27 and fed directly to the discharging port. Further, if a face-down designation is given from the controller part, the transferring material 2 is led by the flapper 31 to the rollers 28 and the rollers 29, and is conveyed till a trailing end of the transferring material 2 passes the rollers 28. Thereafter, the rollers 29 rotate reversely, and the transferring material 2 is fed in, with its trailing end headed, towards the rollers 30 and thus conveyed to the discharging port.
Note that the numeral 36 represents a density sensor, 37 designates a color deviation sensor, and 38 denotes a driving roller in FIG. 6.
FIG. 7 is a block diagram showing a system architecture of the printer P illustrated in FIG. 6. In FIG. 7, there are shown a host computer 200, a controller part 201, a discharging option control part 202 and an engine control part 203. The engine control part 203 includes a video interface part 204, a CPU (Central Processing Unit) 205, an image processing GA 206, an image control part 207, a fixing control part 208, a transferring material conveying part 209 and a driving control part 210.
The controller part 201 is mutually communicable with the host computer 200, the discharging option control part 202 and the engine control part 203. The controller part 201 receives image information and a print command from the host computer 200, analyzes the received image information and converts the image information into bit data. The controller part 201 transmits, for every transferring material, a scheduled print command, a print start command and video signals to the engine control part 203 via the vide interface part 210. Further, at this time, the controller part 201 also transmits, based on an instruction given from the host computer 200, an instruction signal relating to the use of the discharging control option 26 to the discharging option control part 202.
The controller part 201 sends the scheduled print command to the engine control part 203 in accordance with the print command given from the host computer 200, and sends the print start command to the engine control part 203 at a timing when a printable status occurs.
The engine control part 203 performs print executing preparations in the order indicated by the scheduled print command sent from the controller part 201, and waits for the print start command to be issued from the controller part 201. The engine control part 203, upon receiving the print instruction signal, outputs a /TOP signal serving as a reference timing for outputting the video signals to the controller part 201, and starts a print operation as the scheduled print command instructs.
FIG. 8 is a flowchart showing a flow of the print operation of the engine control part 203 shown in FIG. 7.
The engine control part 203, when receiving the scheduled print command, waits for receiving the print start command (step S801), and executes pre-processing (which will hereinafter be termed an initial rotation sequence) for conducting the print operation (step S802). The engine control part 203, after an end of the initial rotation sequence, outputs the /TOP signal and starts the print operation (sequence) according to the scheduled print command of the first sheet (step S803).
The engine control part 203, if a next scheduled print command is not received (step S805) till a next print operation start timing (which will hereinafter be referred to as a normal print start timing) for maintaining a throughput (step S804), executes post-processing (which will hereinafter be termed a post-rotation sequence) of the print operation (step S809), and thereafter finishes the present print operation.
While on the other hand, if the next scheduled print command is received (step S805) till the next normal print start timing (step S804), and if a print start command for the scheduled print command is received (step S806), the engine control part 203 starts the print operation of the second sheet subsequent to the first sheet (step S803).
Further, if the scheduled print command is received (step S805) till the next normal print start timing (step S804), and if the print start command is not received (step S806), the engine control part 203 executes the post-rotation sequence (step S807) and comes to a print start command waiting status (step S808). Then, the engine control part 203, after waiting for receiving the print start command, starts the initial rotation sequence (step S802).
Next, a duplex printing operation in a case where the discharging option 26 is designated at a discharging port in the printer P shown in FIG. 6, will be explained referring to FIGS. 9 and 10.
Herein, the duplex printing operations of three sheets (6-page printing) to the discharging option 26 from a transferring material cassette 1 will be described.
FIG. 9 is a diagram of a communication sequence of the controller part 201 in the case of effecting the duplex printing in the printer P shown in FIG. 6.
The controller part 201 alternately transmits, to the engine control part 203, the scheduled print command from the transferring material cassette 1 (referred to as “C” in FIGS. 1, 2, 9, 11 and 12) to the duplex unit (referred to as “U” in FIGS. 1, 2, 9, 11 and 12) and the scheduled print command from the duplex unit to the discharging option (referred to as “O” in FIGS. 1, 2, 9, 11 and 12) 26 (S911, S912, S913, S914, S915, S916). Then, the controller part 201 transmits to the discharging option control part 202, a scheduled discharging command 1 in S901, a scheduled discharging command 2 in S903 and a scheduled discharging command 3 in S905, respectively. The controller part 201, after transmitting the scheduled discharging command 1 in S901, the scheduled discharging command 2 in S903 and the scheduled discharging command 3 in S905, acquires from the discharging option control part 202 a discharging interval at which a next transferring material becomes receivable since a transferring material with the discharging option 26 scheduled has been received (S902, S904). Thereafter, the controller part 201 sends the print start command of the first sheet to the engine control part 203 (S917).
The engine control part 203, upon receiving the print start command 1 from the controller part 201 (S917), executes the initial rotation sequence, then starts the print operation by outputting a /TOP signal 1 to the controller part 201 (S918), and conveys the transferring material to the duplex unit from the transferring material cassette 1.
The controller part 201 outputs the video signals in synchronization with the /TOP signal 1 received from the engine control part 203, and outputs the print start command 2 for the next scheduled print command 2 in S912 (S919).
The engine control part 203, upon receiving the print start command 2 from the controller part 201 (S919), transmits a /TOP signal 2 to the controller part 201 at the normal print start timing of the second sheet (S920). Then, the engine control part 203 continues the print operation of the scheduled print command 2 in S912 subsequent to the first sheet, and conveys the transferring material to the discharging option 26 from the duplex unit.
Hereafter, similarly, the engine control part 203, when receiving the print start command till the normal print start timing, continues the print operation in the order designated by the print schedule.
Note that the case of receiving the print start command after having already made the print schedule is herein explained, however, the controller part 201 is capable of continuing the consecutive printing by transmitting the scheduled print command and the print start command of the next page till the normal print start timing during the consecutive printing.
FIG. 10 is a timing chart showing an operation timing of the engine control part 203 in the case of performing the duplex printing in the printer P illustrated in FIG. 6.
The engine control part 203, when receiving from the controller part 201 the print start command 1 for the scheduled print command of the first sheet (S1011), starts the initial rotation sequence. During this initial rotation sequence, the engine control part 203, after an end of the initial rotation sequence, start the print operation of the first sheet by outputting the /TOP signal 1 (S1021), and conveys the transferring material to the duplex unit from the transferring material cassette 1.
The engine control part 203, in the case of receiving the print start command 2 (S1012) till the normal print start timing of the second sheet (S1002) after transmitting the /TOP signal 1 of the first sheet (S1021), starts the print operation of the second sheet subsequent to the first sheet by outputting the /TOP signal 2 (S1022) at the normal print start timing of the second sheet (S1002), and conveys the transferring material to the discharging option 206 from the duplex unit.
Thereafter, the engine control part 203, in the case of receiving the scheduled print command and the print start command of the next page till the normal print start timing, continues the consecutive printing by outputting the /TOP signal.
While on the other hand, in the case of receiving neither the scheduled print command nor the print start command of the next page till the normal print start timing (during a period of S1006–S1007), the engine control part 203 starts the post-rotation sequence, and finishes the print operation.
Next, a print operation in the case of stapling the transferring materials discharged to the discharging option 26 when conducting the duplex printing to the discharging option 26 from the transferring material cassette 1 in the printer P illustrated in FIG. 6, will be described with reference to FIGS. 11 and 12.
Given herein is an explanation of an operation in the case of stapling at a point of time when the second sheet is discharged to the discharging option 26 on the occasion of the duplex printing of three sheets (6-page printing) to the discharging option 26 from the transferring material cassette 1 in the same way as FIGS. 9 and 10 shows.
FIG. 11 is a diagram of a communication sequence of the controller part 201 in the case of stapling during the duplex printing in the printer P shown in FIG. 6.
The controller part 201 alternately transmits, to the engine control part 203, the scheduled print command from the transferring material cassette 1 to the duplex unit and the scheduled print command from the duplex unit to the discharging option 26 (S1111, S1112, S1113, S1114, S1115, S1116). Then, the controller part 201 transmits to the discharging option control part 202 a scheduled discharging command 1 in S1101, a scheduled discharging command 2 in S1103 and a scheduled discharging command 3 in S1105, respectively.
The controller part 201, when transmitting the scheduled discharging command 1 in S1101, the scheduled discharging command 2 in S1103 and the scheduled discharging command 3 in S1105, acquires from the discharging option control part 202 a discharging interval at which a next transferring material becomes receivable since a transferring material with the discharging option scheduled has been received (S1102, S1104, S1106).
Thereafter, the controller part 201 transmits the print start command 1 to the engine control part 203 (S1117), whereby the engine control part 203 starts the print operation by outputting the /TOP signal 1 of the first sheet (S1112), and conveys the transferring material to the duplex unit from the transferring material cassette 1.
As for the pages from the second page onwards, the controller part 201 transmits the scheduled print command and the print start command till the normal print start command, whereby the engine control part 203 can continue the consecutive printing by outputting the /TOP signal at the normal print timing.
Concerning the third sheet, i.e., “a transferring material corresponding to a scheduled print 6 in S116”, discharged to the discharging option 26, however, the print of the third sheet can not be started during a period, i.e., “a period of a discharging interval 2 (A)”, for which the discharging option 26 can receive the third sheet with an end of stapling of the second sheet, i.e., “a transferring material corresponding to a scheduled print 4 in S1114”.
Accordingly, the controller part 201 is required to transmit the print start command of the third sheet of “transferring material corresponding to the scheduled print 6 in S1116” so that a print interval between the second sheet of “transferring material corresponding to the scheduled print 4 in S1114” and the third sheet of “transferring material corresponding to the scheduled print 6 in S1116” is longer than a discharging interval A in S1104 that has been acquired when making a schedule of the second sheet of “transferring material corresponding to the scheduled print 4 in S1114 which has been discharged to the discharging option 26 last time” with respect to the discharging option 26.
At this time, if the controller part 201 transmits the print start command till the normal print start timing, the engine control part 203 starts the print operation at the normal interval (which continues the consecutive printing without expanding an interval between the transferring materials), and hence it follows that the second and third sheets of transferring materials collide with each other within the discharging option 26.
FIG. 12 is a timing chart showing an operation timing of the engine control part 203 in the case of effecting stapling during the duplex printing in the printer P shown in FIG. 6.
The controller part 201 transmits to the engine control part 203 the print start command of the third sheet of “transferring material corresponding to the scheduled print 6 in S1216” after an elapse of the sheet discharging interval A in S1230 since the print start timing (S1204) of the second sheet of “transferring material corresponding to the scheduled print 4 in S1214”.
If a timing (S1207) at which the discharging interval A in S1230 elapses since the print start timing of the second sheet of “transferring material corresponding to the scheduled print 4 in S1214” is posterior to the normal print timing (S1206) of the third sheet of “transferring material corresponding to the scheduled print 6 in S1216”, the engine control part 203 temporarily executes the post-rotation sequence at a point of time of S1206.
Thereafter, the engine control part 203 starts the initial rotation sequence after waiting for receiving the print start command in S1216, of the third sheet of “transferring material corresponding to the scheduled print 6 in S1216”.
Further, Japanese Patent Application Laid-Open Publication No. 2001-88370 discloses a conventional technology related to the image forming apparatus pertaining to the scheduled print.
In the sequence in the conventional image forming apparatus described above, however, the post-rotation sequence is executed before starting the print operation corresponding to the scheduled print 6. Therefore, the print operation corresponding to the scheduled print 6 in S1216 can be originally started after the sheet discharging interval A (just when in S1207) since the print start timing (S1204) of the scheduled print 4, and nevertheless a downtime elongates as much as a period of the point of time in S1207 through the end (S1208) of the initial rotation sequence.
It is required for eliminating the downtime to control so as not to execute the post-rotation sequence till the discharging interval A (till the point of time in S1207) since the print start timing (S1204) of the scheduled print 4, and this control was hard to perform.